Grover Underwood

In the first movie, Grover is Percy's best friend at school and hides that he's a satyr. After the Fury shows up at the museum, he takes Percy and Sally toward camp. He travels with his friend and Annabeth across the country and uses Medusa's head against a Hydra. In the Underworld, the group has pearls for only three. Grover volunteers to stay. Persephone, who admires him, is the goddess they meet down there.

In the second movie, Grover senses where the Golden Fleece is, and the feeling points to the Florida coast. Demigods allied with Luke kidnap him and take him to a yacht. Later he turns up on Polyphemus's island disguised as a female Cyclops so he won't become dinner. Percy and the others rescue him, and Grover returns to camp with the group.

In the series, Grover is the satyr who has looked after Percy since school and dreams of finding the god Pan. He goes with Percy and Annabeth across the country. At the Lotus Casino, an old acquaintance says he found Pan, and the trio stays trapped there for days without noticing. Crossing the Underworld, Grover loses the pearl he was carrying. All he wants is for his friend to reach Olympus alive.

In S2, Grover disappears, and Percy dreams of him surrounded by Luke's demigods. He ends up trapped on the Cyclops Polyphemus's island. When Clarisse arrives, Grover tries to get her out another way but forgets his disguise when Polyphemus returns. Percy and Annabeth find him in the cave, and the group has to flee the Cyclops and a lure that looks like treasure.

Grover comes from Rick Riordan's books and has been Percy's most loyal friend since The Lightning Thief. Brandon T. Jackson played him in the movies; Aryan Simhadri plays him in the series.